This invention relates to camp lanterns and, more particularly, to a valve for operating a camp lantern comprising a minimum of parts and producable economically in commercial quantities.
A typical camp lantern comprises a tank assembly for holding the fuel and contains a built-in air pump for pressurizing the fuel. The fuel is supplied under pressure through a metering valve assembly which typically has three positions, OFF, START and RUN. The fuel (or fuel and air in the START mode) rises under pressure through a generator tube and is injected into an air conduit or air intake tube which is ultimately connected to several mantles at which the actual combustion and light generation takes place.
In the RUN mode of operation, fuel under pressure is supplied through the valve assembly to the generator section which is heated by the combustion taking place in the mantles. In this generator section, the liquid fuel is evaporated into a gaseous form and is sprayed under pressure into the air intake tube. This air intake tube is a vertical cylindrical tube open at the bottom for receiving air and connected at the top to one or several mantles. Air rises in this tube partly because of the heat generated by the combustion at the mantles and partly because of the action of the evaporated fuel being sprayed upwardly into this tube. The result is a fuel-air mixture which is carried to the mantles. The mantles provide heat as well as light and are located in close proximity to the generator and the air intake tube, thus providing for the steady state operation of the lantern in the RUN position by preheating the fuel air mixture.
To start the lantern, heat must initially be supplied to the generator and air intake tube sections. This is done by providing the valve assembly with a START capability comprising a mechanism for supplying air as well as fuel to the generator section. This mechanism in the prior art has been either a separate air valve or an integral part of the valve assembly itself. Air and fuel under pressure are both supplied from the tank assembly to the generator section, the resultant combustion mixture being sprayed directly into the air intake tube for combustion at the mantles. Combustion at the mantles proceeds under this mode of operation until the generator section has been heated to the point where it will vaporize the fuel contained therein. At that point, the valve is positioned to its RUN position, cutting off the flow of air from the tank assembly into the generator. From this position, the valve supplies only fuel, air rises in the air intake tube automatically, and the RUN mode of operation is thus initiated and maintained.
At the top of the generator a cap is provided which has an orifice in the order of about eight thousandths of an inch diameter in the described embodiment. Partly because of impurities in the fuel supply and partly because some combustion takes place at this generator orifice, especially at the time when the lantern is turned OFF, it is common for this generator orifice to become blocked. Thus, it is necessary that camp lanterns be supplied with some kind of cleaning needle to periodically clear this orifice.
One method of clearing this orifice has been to supply the lantern with a cleaning tool in the form of a correctly sized needle and a mechanism for driving said needle into and out of the orifice. This needle mechanism is conveniently built into the lantern. See, for instance, U.S. Pat. No. 3,529,911.
In an improved prior art camp gas stove, a cleaning needle is coupled to the flow adjustment valve so that this cleaning is accomplished automatically. In this embodiment a rotating flow valve is used to open and close the fuel intake line. In intermediate positions, it varies the fuel flow rate to the stove burner. A rod couples the cleaning needle to the flow valve so that when the valve is fully closed, the needle is forced into the orifice, but when the valve is opened to allow the lantern to function in its normal operating range, the needle is withdrawn from the orifice. In this case, the needle cleaning mechanism is automatically driven by the flow valve mechanism. In the lantern embodiment disclosed herein, there is no flow valve.
There are three requirements that must be accomplished by the valve assembly and ancillary mechanisms in a camp lantern. The valve assembly must supply an air fuel mixture to the generator in the START mode, it must supply fuel to the generator in the RUN mode, and the valve assembly or ancillary apparatus must be provided to periodically clear the generator orifice. The valve and orifice cleaning apparatus frequently comprise a large number of parts and contribute to the unreliability and difficulty in use of the typical camp lantern. What is required is a camp lantern valve assembly which is convenient in operation and which uses a minimum number of parts so that the unit may be mass produced economically.